The present invention relates to a cover for a housed thermostat comprising a thermostat valve which is held on the cover, forms a main valve and a short-circuit valve, and contains a thermostatic working element the housing of which is connected with a main valve disk which is loaded by a closing spring in the direction of a valve seat, the closing spring being supported on holding devices connected with the cover.
A cover of the above-described type is shown, for example, in German Patent Document DE-U 88 797.4, and forms a constructional unit together with the thermostat valve. This constructional unit can be tested separately, that is, without being installed into the housing, with respect to the tightness of the main valve. In the cover shown in the German Patent Document, a main valve disk made of sheet metal is fastened to the housing of the thermostatic working element. The closing spring of the main valve disk is supported against a bow which is hung into finger-type holding elements which are molded onto the cover. The housing of the thermostatic working element is lengthened by means of a metallic pin on which a short-circuit valve disk with a slideway is arranged. The short-circuit valve spring is situated between this valve disk and the housing of the working element.
German Patent Document DE-U 91 04 964.4 shows a main valve disk of a thermostat valve manufactured as a plastic molded part which is held on the housing of the thermostatic working element in a form-locking manner. The sealing surface of the main valve disk is provided with a recess into which a sealing ring is inserted.
German Patent Document DE-U 88 08 932.0 shows the fastening of a sleeve on the housing of the thermostatic working element which forms a slide for a slide valve. By means of its end, this sleeve dips into a recess of a housing.
German Patent Document DE-U 87 00 216.7 shows the fitting of a cap-type part on the end of a housing of a thermostatic working element, which part forms a chamber with the housing in which an electric heating element is arranged in the form of a PTC-resistance.
It is also known, in the case of thermostat valves, to guide the short-circuit valve disk on several pins which are fastened to the main valve disk. These pins are surrounded by pressure springs against the force of which the short circuit valve disk can be slid on the pins.
An object of the present invention is to provide a cover for a housed thermostat of the initially mentioned type in such a manner that the manufacturing costs are reduced.
This and other objects are achieved by the present invention which provides a cover for a housed thermostat, the housed thermostat having a thermostat valve which is held on the cover and forms a main valve and a short-circuit valve. The thermostat valve contains a thermostatic working element with a housing and a main valve disk connected with the housing of the thermostatic working element. The cover comprises a projection molded to the main valve disk and is a molded plastic part that surrounds the housing of the working element in a cage-type manner. An end of the projection projects over the housing of the working element and forms a part of the short-circuit valve.
The present invention retains the advantage that the cover forms a constructional unit with the thermostat valve which can be tested separately, particularly with respect to the tightness of the valve seat (leakage) and function, before it is installed into the housed thermostat. The design of the main valve disk makes it possible to combine the short circuit valve with the main valve disk, without the requirement that the thermostatic working element has to accommodate any parts for the short circuit valve. It is therefore easily possible to use the same thermostatic working element for thermostat valves with or without a short-circuit valve. Furthermore, shaped sheet metal parts are avoided which require increased manufacturing expenditures and which must be made of an expensive material because they must be resistant to corrosion.
In a first embodiment of the present invention, a pin is molded onto the projection of the main valve disk on which a short-circuit valve disk is guided. This short-circuit valve disk may be made of sheet metal or plastic.
In another embodiment of the present invention, the projection of the main valve disk has a bottom with a surrounding closed ring which is used as a shorting plunger. In this embodiment, the short-circuit valve is constructed as a sliding valve, the shorting plunger dipping into a corresponding bore of the housing. In order to guide the shorting plunger and to center it in the bore of the housing, it is provided in a further embodiment of the invention that the ring is extended in the axial direction by means of guide fingers.
In another embodiment of the invention, the cover is equipped with molded-on holding fingers which extend essentially in parallel to the longitudinal direction of the housing and have receiving devices pointing to the center for the support of the closing spring.
In another embodiment of the invention, an insert is mounted on the cover which is constructed as a plastic molded part and which forms an abutment for the closing spring. Also in this embodiment, the cover together with the thermostat forms a preassembled constructional unit which can therefore be tested with respect to the tightness of the valve seat and the function, while the abutment for the closing spring is not molded onto the cover.
In another embodiment, the insert has a lengthening which is equipped with window-type recesses and in which the projection of the main valve disk is guided which has a surrounding bottom with a surrounding closed ring which forms a short-circuit sliding valve with the lower edges of the window-type recesses of the insert. In this embodiment, the short-circuit sliding valve is integrated into the constructional unit which is preassembled with the cover so that the closing temperature is independent of any tolerances or the like of the housing. It need only be provided that the insert is sealingly inserted into the short-circuit line of the housing which does not present any difficulty also in the event of relatively large permissible tolerances.
In order to provide a thermostat valve which can be adjusted in a simple manner to different opening temperatures, an embodiment of the present invention provides the projection of the main valve disk with a bottom, the projection forming a chamber with the end of the housing of the thermostatic working element in which an electric heating element is arranged which rests against the bottom of the housing As a result, it becomes possible to adjust the thermostatic working element to a high opening temperature by the selection of its wax filling and nevertheless cause an opening in the case of a lower coolant temperature. By the electric heating of the thermostatic working element, a mixed temperature will then be obtained from the coolant temperature and the temperature generated by the electric heating which "simulates" to the thermostatic working element an increased coolant temperature so that this working element already opens despite the lower coolant temperature
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.